Large Observatory for x-ray Timing (LOFT-P): a Probe-class mission concept study

Abstract

LOFT-P is a mission concept for a NASA Astrophysics Probe-Class (<$1B) X-ray timing mission, based on the LOFT M-class concept originally proposed to ESAs M3 and M4 calls. LOFT-P requires very large collecting area, high time resolution, good spectral resolution, broad-band spectral coverage (2-30 keV), highly flexible scheduling, and an ability to detect and respond promptly to time-critical targets of opportunity. It addresses science questions such as: What is the equation of state of ultra dense matter? What are the effects of strong gravity on matter spiraling into black holes? It would be optimized for sub-millisecond timing of bright Galactic X-ray sources including X-ray bursters, black hole binaries, and magnetars to study phenomena at the natural timescales of neutron star surfaces and black hole event horizons and to measure mass and spin of black holes. These measurements are synergistic to imaging and high-resolution spectroscopy instruments, addressing much smaller distance scales than are possible without very long baseline X-ray interferometry, and using complementary techniques to address the geometry and dynamics of emission regions. LOFT-P would have an effective area of >6 m 2 , > 10× that of the highly successful Rossi X-ray Timing Explorer (RXTE). A sky monitor (2-50 keV) acts as a trigger for pointed observations, providing high duty cycle, high time resolution monitoring of the X-ray sky with ∼20 times the sensitivity of the RXTE All-Sky Monitor, enabling multi-wavelength and multimessenger studies. A probe-class mission concept would employ lightweight collimator technology and large-area solid-state detectors, segmented into pixels or strips, technologies which have been recently greatly advanced during the ESA M3 Phase A study of LOFT. Given the large community interested in LOFT (>800 supporters * , the scientific productivity of this mission is expected to be very high, similar to or greater than RXTE (∼ 2000 refereed publications). We describe the results of a study, recently completed by the MSFC Advanced Concepts Office, that demonstrates that such a mission is feasible within a NASA probe-class mission budget.

Gravitational waves from neutron star mergers and their relation to the nuclear equation of state

“…Future observations by the NICER (Neutron star Interior Composition Explorer) mission [660,62], expected to provide first results within this year, and the planned eXTP (enhanced x-ray Timing and Polarimetry) Mission [65], LOFT (Large Observatory For x-ray Timing) satellite [661], and ATHENA (Advanced Telescope for High Energy Astrophysics) [662] are seen to have completely different systematic errors, and thus, by combining many measurements with differing systematics one can hope to significantly narrow the range for R 1.4 . These endeavours are based on the idea of measuring pulsations in the x-rays emitted from the hot polar cap of a pulsar due to its rotation.…”

STROBE-X: X-ray timing and spectroscopy on dynamical timescales from microseconds to years

“…Continuous telemetry of the WFM data will make it a powerful instrument in its own right. STROBE-X builds upon the X-ray timing results, existing technologies, and community built from the Rossi X-ray Timing Explorer (RXTE, 1995-2012, [4]), the Large Observatory For x-ray Timing (LOFT, [5,6]), studies for the Advanced X-ray Timing Array (AXTAR, [7]) and LOFT-Probe (LOFT-P, [8]), and the Neutron star Interior Composition Explorer (NICER, 2017-present, [9]). The X-ray concentrator optics, fully developed for NICER, are scaled up with longer focallengths to provide large collecting area with low background at low cost.…”

Unveiling the correlations of tidal deformability with the nuclear symmetry energy parameters

“…The precise observations of high mass pulsars such as PSR J1614 − 2230 (1.908 ± 0.016 M ) [4], PSR J0348 + 0432 (2.01 ± 0.04 M ) [5] and the recently detected millisecond pulsar J0740 + 6620 (2.14 +0.10 −0.09 M ) [6] have already put tight bounds on nuclear matter EoS. Along with precise measurement of the NS masses, future observations such as those planned by NICER (Neutron star Interior Composition Explorer) mission [7,8], eXTP (enhanced X-ray Timing and Polarimetry) Mission [9], LOFT (Large Observatory For X-ray Timing) satellite [10], and ATHENA (Advanced Telescope for High Energy Astrophysics) [11] may provide besides the mass also the possible range for the radius (R 1.4 ) of a canonical NS (M = 1.4M ) and other selected NS. The current empirical estimates of R 1.4 is 11.9 ± 1.22 km [12][13][14][15][16].…”